1. Field of Use
The present invention relates generally to the field of seating. More particularly, the present invention concerns a method of assembling a seat that includes a seat shell. Specifically, a preferred embodiment of the present invention is directed to the assembly of a seat that includes a flexible seat shell and cushions. The present invention thus relates to methods of assembling seats of the type that can be termed flexible seat shell seats.
2. Description of Related Art
Within this application several publications are referenced by arabic numerals within parentheses. Full citations for these publications may be found at the end of the specification immediately preceding the claims. The disclosures of all these publications in their entireties are hereby expressly incorporated by reference into the present application.
Heretofore, it was known in the prior art to provide a seat having a separate back and base. A conventional seat is typically assembled by providing two separate cushions (i.e., a back cushion and a base cushion) together with a frame. For example, a conventional seat can be assembled by bolting, or screwing, one of the two separate cushions to a tubular steel frame followed by bolting, or screwing, the other cushion to the tubular steel frame.
A previously recognized problem has been that the time required for assembly a seat having two separate cushions is lengthy. What is needed therefore is way of assembling the seat that requires less time.
Heretofore, it was also known in the prior art to attach cushions to a seat frame with fasteners. For example, a conventional seat can be assembled by bolting, or screwing, one of the two separate cushions to a tubular steel frame followed by bolting, or screwing, the other cushion to the tubular steel frame.
A previously recognized problem has been that numerous fasteners are required for assembling such a seat. What is also needed therefore is way of assembly that requires fewer fasteners.
Heretofore, it was also known in the prior art to injection mold the various parts of a seat. For example, the cushions of seats have been known to include a plastic ring that permits mounting screws to be driven into the cushion with resiliency. Such a conventional plastic ring is typically injection molded at high pressure in a large metal mold.
A previously recognized problem has been that tooling for injection molding is expensive. What is also needed therefore is an inexpensive way of molding plastic parts for inclusion in a seat.
Heretofore these requirements have not been fully met without incurring various disadvantages.
One unsatisfactory previously recognized solution to the problems of using a separate back and base was to injection mold a unitary seat shell. By combining the back and base into one unit, the time required for assembly is reduced. As noted above, a disadvantage of this previously recognized solution is that injection mold tooling is expensive. Further, this previously recognized solution also has the disadvantage that some fasteners are still required to attach the seat shell to the frame.
Heretofore, it was known in the prior art to thermoform a sheet of plastic. Methods of thermoforming plastic are described in "Thermoforming" by James L. Throne, Hanser Publisher, New York (1987) and in "Guide to Extruded Plastic Sheet Products" by the Society of Plastic Industry, (1988). For example, a sheet of thermoplastic is typically thermoformed with a vacuum thermoform mold.
A previously recognized problem with thermoforming has been that thermoforming is limited to fabricating shapes of limited relief. If the amount of relief is too high, impermissible thinning of the thermoplastic material thickness results in the high relief sections of the mold. Further, if the amount of relief is too high, the decorative embossment of the thermoplastic is disrupted in the high relief sections of the mold. For example, a rigid unitary seat shell is a high relief design because of the angular junction between the back of the seat and the base of the seat. In the case of a high relief shape such as a unitary seat shell, thermoforming the finished shape results in an impermissibly thin edge at the junction of the back section and the base section because of the amount of draw required to form the angular junction between the back of the seat and the base of the seat. Moreover, the decorative embossment of the thermoplastic material would be unattractively disrupted at both the top of the back and at the front of the base because of the amount of draw required to form the angular junction.
The below-referenced prior patents disclose embodiments that were satisfactory for the purposes for which they were intended but which had disadvantages. The disclosures of all the below-referenced prior patents in their entireties are hereby expressly incorporated by reference into the present application.
U.S. Pat. No. 5,344,215 discloses a backrest recliner mechanism. U.S. Pat. No. 5,183,314 discloses a concealed mechanism for detachably mounting a vehicle seat. U.S. Pat. No. 5,176,356, discloses a suspension for a vehicle seat. U.S. Pat. No. 4,836,609 discloses a unitary shell for a vehicle seat. U.S. Pat. No. 4,726,086 discloses a composite foam seat cushion. U.S. Pat. No. 4,647,109 discloses a upholstered seat assembly and a one-piece seat and back shell of molded plastic. U.S. Pat. No. 4,405,681 discloses a foam cushion. U.S. Pat. No. 3,740,014 discloses an adjustable seat assembly for a vehicle.
In embodiments disclosed in the above-referenced prior patents without unitary seat shells, the back and base cushions of the seats are disclosed as being separately connected to the underlying frame. Such a non-unitary approach has the disadvantage that assembly costs are increased due to the above-discussed increase in the number of fasteners required for assembly, as well as the above-discussed increase in the time required for assembly. Those embodiments disclosed in the above-reference prior patent having unitary seat shells have the disadvantage that expensive tooling is required to injection mold the seat shells. Further, a certain number of separate assembly fasteners are still required to attach such injection molded unitary seat shells to the underlying flames.